FIELD OF THE ART
The invention relates to a control bar drive device for a nuclear reactor cooled by a pressurized fluid, of the type having a control bar guide placed above the reactor core, a casing containing a drive mechanism and connected to the inside of a reactor vessel by a sheath passing sealingly through a lid of the vessel containing the reactor core, a drive shaft movable vertically within and along the sheath, connecting the mechanism to the bar and passing, with a radial clearance, through an upper closure plate of the guide, a heat protection sleeve being interposed radially between the shaft and the sheath and having an end piece co-operating with said upper plate for controlling a coolant flow.